Aposhitehyid; gazan is a term they use to denote geza’ah, stock; it is exclusive to chabad, and you won’t hear it in the kiruv circles. It’s a status for shiduchim, that even a chabad chossid whose grandparents were chabad, but they originally were skver, belz or whatever, then they will not do a shidduch with someone whose ancestors were originally Russian lubavitchers. This is silly because original chabad chasidim were not always chabad, since beforehand they were Litvish, but it’s more than silly, it’s supremacist and elitist, but much moreso than the norm of lifestyle/rebbishe/rosh yeshivishe families. Those are categories that are made to ensure that the couple get along, or for the kovod of Torah or rebbishe bloodlines. Here it’s simple geography that determines ones worthiness. In chabad, a rosh yeshiva whose grandparents were belz cannot marry an am haaretz whose grandparents were chabad.
Besides that, it runs totally against what they preach in the open about accepting every jew. I totally understand not marrying into families with pgam in their yichus, bnei nidah, gerim, and other things that actually have mekoros in the seforim – happens to be that gedolei yisroel have downplayed these concerns for quite some time, with rav moshe writing to disregard ben nidah as an issue if the boy is a ben Torah with good middos.
What chabad are saying is that the secular jew with the ponytail is no different than one of us, and we’ll get him to become frum, but he IS different regarding who he can marry. He is lower class. He is confined to BTs, no matter how much he’s shteiged. In contrast, a BT in the yeshiva world who has shed his former life and embraced learning fully with no remnant of his past will not be shut out. I know BTs of that caliber who married very choshuve families, because we have a meritocracy to a large degree.
Legitimate criticism doesn’t always come from having bad experiences. The only bad experiences I’ve had have been hearing avodah zara from them and having their missionaries descend on my neighborhood and yeshiva over the years.